adds a few plotting utils
adds gradients to barycentric code
first pass at linear approx HJB idea
adds stand-alone function approximator demo, to be merged with drakeFunctions
adds quadrotor wrl model
movied hjb idea to dev directory
touch-ups from Twan's code review
Merge pull request #411 from RussTedrake/lecture04

updates from 6.832 class prep / demos